package LeetCode.exercise;

import java.util.LinkedList;
import java.util.Queue;

public class LC200 {
    int[] dx = {0, 0, 1, -1};
    int[] dy = {1, -1, 0, 0};
    int m, n;
    boolean[][] flag;
    public int numIslands(char[][] grid) {
        m = grid.length;
        n = grid[0].length;
        flag = new boolean[m][n];
        int res = 0;
        for(int i = 0; i < m; i++){
            for(int j = 0; j < n; j++){
                if(grid[i][j] == '1' && !flag[i][j]){
                    res++;
                    bfs(grid, i, j);
                }
            }
        }
        return res;
    }

    public void bfs(char[][] grid, int i, int j) {
        Queue<int[]> q = new LinkedList<>();
        q.offer(new int[]{i, j});
        flag[i][j] = true;
        while(!q.isEmpty()){
            int[] tmp = q.poll();
            int a = tmp[0], b = tmp[1];
            for(int k = 0; k < 4; k++){
                int x = a + dx[k], y = b + dy[k];
                if(x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == '1' && !flag[x][y]){
                    q.offer(new int[]{x, y});
                    flag[x][y] = true;
                }
            }
        }
    }
}
